Method and system of monitoring, sensor validation and predictive fault analysis

Abstract

The present invention provides an improved method and system for real-time monitoring, validation, optimization and predictive fault analysis in a process control system. The invention monitors process operations by continuously analyzing sensor measurements and providing predictive alarms using models of normal process operation and statistical parameters corresponding to normal process data, and generating secondary residual process models. The invention allows for the creation of a fault analyzer directly from linearly independent models of normal process operation, and provides for automatic generation from such process models of linearly dependent process models. Fuzzy logic is used in various fault situations to compute certainty factors to identify faults and/or validate underlying assumptions. In one aspect, the invention includes a real-time sensor data communications bridge module; a state transition logic module; a sensor validation and predictive fault analysis module; and a statistical process control module; wherein each of the modules operates simultaneously.

1. A method of monitoring, validation and analysis for a process control system having normal process data and sensors, and represented by a plurality of primary process models and a plurality of process variables, comprising:
 generating a plurality of primary residual process models derived from said primary process models, said normal process data, and one or more statistical parameters corresponding to said normal process data; 
 measuring real-time sensor data; 
 computing primary residual values of said primary residual process models corresponding to said real-time sensor data; 
 deriving an expected value for one or more of said primary residual values from historical normal process data; 
 determining deviations of said primary residual values from said corresponding expected values; 
 mapping one or more of said deviations of said primary residual values from said corresponding expected values into one or more compressed values; 
 automatically generating one or more fuzzy logic diagnostic rules; 
 computing a certainty factor for a possible fault by applying said fuzzy logic diagnostic rules to said compressed values; and 
 displaying said certainty factor on a monitor, computer screen or control console used for monitoring, validation and analysis for a process control system. 
 
   
   
     2. The method as set forth in  claim 1 , further comprising:
 measuring said normal process data. 
 
   
   
     3. The method as set forth in  claim 1 , further comprising:
 calculating said statistical parameters. 
 
   
   
     4. The method as set forth in  claim 1 , further comprising:
 computing a certainty factor corresponding to each of said primary residual values. 
 
   
   
     5. The method as set forth in  claim 1  wherein said fuzzy logic is defined in a diagnostic rule that is regenerated each time said diagnostic rule is used. 
   
   
     6. The method as set forth in  claim 1  wherein said fuzzy logic is defined in a diagnostic rule as follows;
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     7. The method as set forth in  claim 6 , further comprising:
 determining a direction of deviation of said primary residual values from said expected values; and 
 determining evidence-for-fault and evidence-against-fault by comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     8. The method as set forth in  claim 6 , further comprising:
 determining neutral-evidence by comparing the magnitude of a deviation of said primary residual values to zero. 
 
   
   
     9. The method as set forth in  claim 1 , further comprising:
 generating one or more secondary residual process models, wherein each of said secondary residual process models is derived from two primary residual process models having at least one common process variable. 
 
   
   
     10. The method as set forth in  claim 9 , further comprising:
 computing secondary residual values of said secondary residual process models corresponding to said real-time sensor data; and 
 comparing said secondary residual values to expected values. 
 
   
   
     11. The method as set forth in  claim 10 , further comprising:
 determining a direction of deviation of said secondary residual values from said expected values; 
 comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     12. The method as set forth in  claim 11  wherein said determination is made by calculating a first partial derivative of said secondary residual process model. 
   
   
     13. The method as set forth in  claim 10 , further comprising:
 computing a certainty factor for a possible fault as a function of one or more of said secondary residual values using fuzzy logic. 
 
   
   
     14. The method as set forth in  claim 13 , further comprising:
 computing a certainty factor corresponding to each of said secondary residual values. 
 
   
   
     15. The method as set forth in  claim 13  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     16. The method as set forth in  claim 15 , further comprising:
 determining neutral-evidence from one or more of said secondary residual process models which do not relate to relevant process variables. 
 
   
   
     17. The method as set forth in  claim 9  wherein said secondary residual process models are functions of both measured process variables and unmeasured process variables. 
   
   
     18. The method as set forth in  claim 9 , further comprising:
 regenerating said secondary residual process models. 
 
   
   
     19. The method as set forth in  claim 1  wherein said statistical parameters comprise a mean and a standard deviation. 
   
   
     20. The method as set forth in  claim 1  wherein said primary residual process models are functions of both a measured process variable and an unmeasured process variable. 
   
   
     21. The method as set forth in  claim 1 , further comprising:
 regenerating said primary residual process models. 
 
   
   
     22. The method as set forth in  claim 1 , further comprising:
 computing a first partial derivative and a second partial derivative of said primary residual process models. 
 
   
   
     23. The method as set forth in  claim 1 , further comprising:
 reporting said certainty factor if it exceeds a predetermined threshold. 
 
   
   
     24. The method as set forth in  claim 1  wherein said certainty factor is between 0.0 and 1.0. 
   
   
     25. The method as set forth in  claim 1 , further comprising:
 evaluating said real-time sensor data using statistical process control charting techniques to determine if a corresponding sensor is in control. 
 
   
   
     26. The method as set forth in  claim 1 , further comprising:
 calculating the exponentially weighted moving average of said real-time sensor data to determine if a corresponding sensor is in control. 
 
   
   
     27. The method as set forth in  claim 1 , further comprising:
 computing a plurality of certainty factors for a corresponding plurality of possible faults. 
 
   
   
     28. A method of monitoring, validation and analysis for a process control system having normal process data and sensors, and represented by a plurality of primary residual process models and a plurality of process variables, comprising:
 measuring real-time sensor data; 
 computing primary residual values of said primary residual process models corresponding to said real-time sensor data; 
 deriving an expected value for one or more of said primary residual values from historical normal process data; 
 determining deviations of said primary residual values from said corresponding expected values; 
 mapping one or more of said deviations of said primary residual values from said corresponding expected values into one or more compressed values; 
 automatically generating one or more fuzzy logic diagnostic rules; 
 computing a certainty factor for a possible fault by applying said fuzzy logic diagnostic rules to said compressed values; and 
 displaying said certainty factor on a monitor, computer screen or control console used for monitoring, validation and analysis for a process control system. 
 
   
   
     29. The method as set forth in  claim 28 , further comprising:
 computing a certainty factor corresponding to each of said primary residual values. 
 
   
   
     30. The method as set forth in  claim 28  wherein said fuzzy logic is defined in a diagnostic rule that is regenerated each time said diagnostic rule is used. 
   
   
     31. The method as set forth in  claim 28  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     32. The method as set forth in  claim 31 , further comprising:
 determining a direction of deviation of said primary residual values from said expected values; and 
 determining evidence-for-fault and evidence-against-fault by comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     33. The method as set forth in  claim 31 , further comprising:
 determining neutral-evidence by comparing the magnitude of a deviation of said primary residual values to zero. 
 
   
   
     34. The method as set forth in  claim 28 , further comprising:
 generating one or more secondary residual process models, wherein each of said secondary residual process models is derived from two primary residual process models having at least one common process variable. 
 
   
   
     35. The method as set forth in  claim 34 , further comprising:
 computing secondary residual values of said secondary residual process models corresponding to said real-time sensor data; and 
 comparing said secondary residual values to expected values. 
 
   
   
     36. The method as set forth in  claim 35 , further comprising:
 computing a certainty factor for a possible fault as a function of one or more of said secondary residual values using fuzzy logic. 
 
   
   
     37. The method as set forth in  claim 36 , further comprising:
 computing a certainty factor corresponding to each of said secondary residual values. 
 
   
   
     38. The method as set forth in  claim 36  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     39. The method as set forth in  claim 38 , further comprising:
 determining neutral-evidence from one or more of said secondary residual process models which do not relate to relevant process variables. 
 
   
   
     40. The method as set forth in  claim 35 , further comprising:
 determining a direction of deviation of said secondary residual values from said expected values; 
 comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     41. The method as set forth in  claim 40  wherein said determination is made by calculating a first partial derivative of said secondary residual process model. 
   
   
     42. The method as set forth in  claim 34 , further comprising:
 regenerating said secondary residual process models. 
 
   
   
     43. The method as set forth in  claim 28 , further comprising:
 regenerating said primary residual process models. 
 
   
   
     44. The method as set forth in  claim 28 , further comprising:
 computing a first partial derivative and a second partial derivative of said primary residual process models. 
 
   
   
     45. The method as set forth in  claim 28 , further comprising:
 evaluating said real-time sensor data using statistical process control charting techniques to determine if a corresponding sensor is in control. 
 
   
   
     46. The method as set forth in  claim 28 , further comprising:
 computing a plurality of certainly factors for a corresponding plurality of possible faults. 
 
   
   
     47. A method of monitoring, validation and analysis for a process control system having normal process data and sensors, and represented by a plurality of primary process models and a plurality of process variables, comprising:
 generating a plurality of primary residual process models derived from said primary process models, said normal process data, and one or more statistical parameters corresponding to said normal process data; 
 automatically generating one or more secondary residual process models, wherein each of said secondary residual process models is derived from two primary residual process models having at least one common variable by combining said primary residual process models to remove any terms containing said common variable; 
 mapping one or more residual values into one or more compressed values; 
 using one or more of said primary residual process models, one or more of said secondary residual process models and said compressed values to predict a possible fault; and 
 displaying said possible fault on a monitor, computer screen or control console used for monitoring, validation and analysis for a process control system. 
 
   
   
     48. The method as set forth in  claim 47 , further comprising:
 measuring said normal process data. 
 
   
   
     49. The method as set forth in  claim 47 , further comprising:
 calculating said statistical parameters. 
 
   
   
     50. The method as set forth in  claim 47 , further comprising: measuring real-time sensor data. 
   
   
     51. The method as set forth in  claim 50 , further comprising:
 computing primary residual values and secondary residual values of said primary residual process models and said secondary residual process models corresponding to said real-time sensor data; 
 comparing said primary residual values and said secondary residual values to expected values; and 
 computing a certainty factor for a possible Fault using fuzzy logic. 
 
   
   
     52. The method as set forth in  claim 51  wherein said fuzzy logic is defined in a diagnostic rule that is regenerated each time said diagnostic rule is used. 
   
   
     53. The method as set forth in  claim 51 , further comprising:
 computing a certainty factor corresponding to each of said primary residual values. 
 
   
   
     54. The method as set forth in  claim 51 , further comprising:
 computing a certainty factor corresponding to each of said secondary residual values. 
 
   
   
     55. The method as set font in  claim 47 , further comprising:
 regenerating said secondary residual process models. 
 
   
   
     56. The method as set forth in  claim 47 , further comprising:
 regenerating said primary residual process models. 
 
   
   
     57. The method as set forth in  claim 47 , further comprising:
 using one or more of said primary residual process models and one or more of said secondary residual process models to predict a plurality of possible faults. 
 
   
   
     58. A method of monitoring, validation and analysis for a process control system having normal process data and sensors, and represented by a plurality of primary process models and a plurality of process variables, comprising:
 generating a plurality of primary residual process models derived from said primary process models, said normal process data, and one or more statistical parameters corresponding to said normal process data; 
 automatically translating said primary residual process models into executable pseudo-code; 
 measuring real-time sensor data; 
 executing said pseudo-code to compute primary residual values corresponding to said real-time sensor data; 
 deriving an expected value for one or more of said primary residual values from historical normal process data; 
 
     determining deviations of said primary residual values from said corresponding expected values; 
     mapping one or more of said deviations into one or more compressed values;
 computing a certainty factor for a possible fault by executing said pseudo-code; and 
 displaying said certainty factor on a monitor, computer screen or control console used for monitoring, validation and analysis for a process control system. 
 
   
   
     59. The method as set forth in  claim 58  wherein said pseudo-code uses fuzzy logic. 
   
   
     60. The method as set forth in  claim 59  wherein said fuzzy logic is defined in a diagnostic rule that is regenerated each time said diagnostic rule is used. 
   
   
     61. The method as set forth in  claim 59  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     62. The method as set forth in  claim 61 , further comprising:
 determining a direction of deviation of said primary residual values from said expected values; and 
 determining evidence-for-fault and evidence-against-fault by comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     63. The method as set forth in  claim 61 , further comprising:
 determining neutral-evidence by comparing the magnitude of a deviation of said primary residual values to zero. 
 
   
   
     64. The method as set forth in  claim 58 , further comprising:
 generating pseudo-code for computing a certainty factor; 
 computing a certainty factor corresponding to each of said primary residual values. 
 
   
   
     65. The method as set forth in  claim 58 , further comprising:
 generating one or more secondary residual process models, wherein each of said secondary residual process models is derived from two primary residual process models having at least one common process variable. 
 
   
   
     66. The method as set forth in  claim 65 , further comprising:
 translating said secondary residual process models into pseudo-code; 
 measuring real-time sensor data; 
 executing said pseudo-code to compute secondary residual values corresponding to said real-rime sensor data; and 
 comparing said secondary residual values to expected values. 
 
   
   
     67. The method as set forth in  claim 66 , further comprising:
 generating pseudo-code for computing a certainty factor; 
 computing a certainty factor corresponding to each of said secondary residual values. 
 
   
   
     68. The method as set forth in  claim 67 , wherein said certainty factor is computed using fuzzy logic. 
   
   
     69. The method as set forth in  claim 65 , further comprising:
 determining neutral-evidence from one or more of said secondary residual process models which do not relate to relevant process variables. 
 
   
   
     70. The method as set forth in  claim 58 , further comprising:
 computing a plurality of certainty factors for a corresponding plurality of possible faults. 
 
   
   
     71. A computer-readable medium having computer-executable instructions for performing a method for a process control system having normal process data and sensors, and represented by a plurality of primary process models and a plurality of process variables, said method comprising:
 generating a plurality of primary residual process models derived from said primary process models, said normal process data, and one or more statistical parameters corresponding to said normal process data; 
 measuring real-time sensor data; 
 computing primary residual values of said primary residual process models corresponding to said real-time sensor data; 
 deriving an expected value for one or more of said primary residual values from historical normal process data; 
 determining deviations of said primary residual values from said corresponding expected values; 
 mapping one or more of said deviations of said primary residual values from said corresponding expected values into one or more compressed values; 
 automatically generating one or more fuzzy logic diagnostic rules; 
 computing a certainty factor for a possible fault by applying said fuzzy logic diagnostic rules to said deviations; and 
 displaying said certainty factor on a monitor, computer screen or control console used for monitoring, validation and analysis for a process control system. 
 
   
   
     72. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 measuring said normal process data. 
 
   
   
     73. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 calculating said statistical parameters. 
 
   
   
     74. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 computing a certainty factor corresponding to each of said primary residual values. 
 
   
   
     75. The computer-readable medium as set forth in  claim 71  wherein said fuzzy logic is defined in a diagnostic rule that is regenerated each time said diagnostic rule is used. 
   
   
     76. The computer-readable medium as set forth in  claim 71  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     77. The computer-readable medium as set forth in  claim 76 , said method further comprising:
 determining a direction of deviation of said primary residual values from said expected values; and 
 determining evidence-for-fault and evidence-against-fault by comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     78. The computer-readable medium as set forth in  claim 76 , said method further comprising:
 determining neutral-evidence by comparing the magnitude of a deviation of said primary residual values to zero. 
 
   
   
     79. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 generating one or more secondary residual process models, wherein each of said secondary residual process models is derived from two primary residual process models having at least one common process variable. 
 
   
   
     80. The computer-readable medium as set forth in  claim 79 , said method further comprising:
 computing secondary residual values of said secondary residual process models corresponding to said real-time sensor data; and 
 comparing said secondary residual values to expected values. 
 
   
   
     81. The computer-readable medium as set forth in  claim 80 , said method further comprising:
 determining a direction of deviation of said secondary residual values from said expected values; 
 comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     82. The computer-readable medium as set forth in  claim 81  wherein said determination is made by calculating a first partial derivative of said secondary residual process model. 
   
   
     83. The computer-readable medium as set forth in  claim 80 , said method further comprising:
 computing a certainty factor for a possible fault as a function of one or more of said secondary residual values using fuzzy logic. 
 
   
   
     84. The computer-readable medium as set forth in  claim 83 , said method further comprising:
 computing a certainty factor corresponding to each of said secondary residual values. 
 
   
   
     85. The computer-readable medium as set forth in  claim 83  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     86. The computer-readable medium as set forth in  claim 85 , said method further comprising;
 determining neutral-evidence from one or more of said secondary residual process models which do not relate to relevant process variables. 
 
   
   
     87. The computer-readable medium as set forth in  claim 79  wherein said secondary residual process models are functions of both measured process variables and unmeasured process variables. 
   
   
     88. The computer-readable medium as set forth in  claim 79 , said method further comprising:
 regenerating said secondary residual process models. 
 
   
   
     89. The computer-readable medium as set forth in  claim 71  wherein said statistical parameters comprise a mean and a standard deviation. 
   
   
     90. The computer-readable medium as set forth in  claim 71  wherein said primary residual process models are functions of both a measured process variable and an unmeasured process variable. 
   
   
     91. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 regenerating said primary residual process models. 
 
   
   
     92. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 computing a first partial derivative and a second partial derivative of said primary residual process models. 
 
   
   
     93. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 reporting said certainty factor if it exceeds a predetermined threshold. 
 
   
   
     94. The computer-readable medium as set forth in  claim 71  wherein said certainty factor is between 0.0 and 1.0. 
   
   
     95. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 evaluating said real-time sensor data using statistical process control charting techniques to determine if a corresponding sensor is in control. 
 
   
   
     96. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 calculating the exponentially weighted moving average of said real-time sensor data to determine if a corresponding sensor is in control. 
 
   
   
     97. The computer-readable medium as set forth in  claim 71 , said method further comprising:
 computing a plurality of certainty factors for a corresponding plurality of possible faults. 
 
   
   
     98. A computer-readable medium having computer-executable instructions for performing a method for a process control system having normal process data and sensors, and represented by a plurality of primary residual process models and a plurality of process variables, said method comprising:
 measuring real-time sensor data; 
 computing primary residual values of said primary residual process models corresponding to said real-time sensor data; 
 deriving an expected value for one or more of said primary residual values from historical normal process data; 
 determining deviations of said primary residual values from said corresponding expected values; 
 mapping one or more of said deviations of said primary residual values from said corresponding expected values into one or more compressed values; 
 automatically generating one or more fuzzy logic diagnostic rules; 
 computing a certainty factor for a possible fault by applying said fuzzy logic diagnostic rules to said deviations; and 
 displaying said certainty factor on a monitor, computer screen or control console used for monitoring, validation and analysis for a process control system. 
 
   
   
     99. The computer-readable medium as set forth in  claim 98 , said method further comprising:
 computing a certainty factor corresponding to each of said primary residual values. 
 
   
   
     100. The computer-readable medium as set forth in  claim 98  wherein said fuzzy logic is defined in a diagnostic rule that is regenerated each time said diagnostic rule is used. 
   
   
     101. The computer-readable medium as set forth in  claim 98  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND) ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     102. The computer-readable medium as set forth in  claim 101 , said method further comprising:
 determining neutral-evidence by comparing the magnitude of a deviation of said primary residual values to zero. 
 
   
   
     103. The computer-readable medium as set forth in  claim 98 , said method further comprising:
 determining a direction of deviation of said primary residual values from said expected values; and 
 determining evidence-for-fault and evidence-against-fault by comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     104. The computer-readable medium as set forth in  claim 98 , said method further comprising:
 generating one or more secondary residual process models, wherein each of said secondary residual process models is derived from two primary residual process models having at least one common process variable. 
 
   
   
     105. The computer-readable medium as set forth in  claim 104 , said method further comprising:
 computing secondary residual values of said secondary residual process models corresponding to said real-time sensor data; and 
 comparing said secondary residual values to expected values. 
 
   
   
     106. The computer-readable medium as set forth in  claim 105 , said method further comprising:
 computing a certainty factor for a possible fault as a function of one or more of said secondary residual values using fuzzy logic. 
 
   
   
     107. The computer-readable medium as set forth in  claim 106 , said method further comprising:
 computing a certainty factor corresponding to each of said secondary residual values. 
 
   
   
     108. The computer-readable medium as set forth in  claim 106  wherein said fuzzy logic is defined in a diagnostic rule as follows:
   FAULT-IS-PRESENT=SOME (evidence-for-fault) AND ALL (neutral-evidence) AND NOT (SOME (evidence-against-fault)). 
 
   
   
     109. The computer-readable medium as set forth in  claim 108 , said method further comprising:
 determining neutral-evidence from one or more of said secondary residual process models which do not relate to relevant process variables. 
 
   
   
     110. The computer-readable medium as set forth in  claim 105 , said method further comprising:
 determining a direction of deviation of said secondary residual values from said expected values; 
 comparing said direction of deviation to an expected direction of deviation consistent with a fault. 
 
   
   
     111. The computer-readable medium as set forth in  claim 110  wherein said determination is made by calculating a first partial derivative of said secondary residual process model. 
   
   
     112. The computer-readable medium as set forth in  claim 104 , said method further comprising:
 regenerating said secondary residual process models. 
 
   
   
     113. The computer-readable medium as set forth in  claim 98 , said method further comprising:
 regenerating said primary residual process models. 
 
   
   
     114. The computer-readable medium as set forth in  claim 98 , said method further comprising:
 computing a first partial derivative and a second partial derivative of said primary residual process models. 
 
   
   
     115. The computer-readable medium as set forth in  claim 98 , said method further comprising:
 evaluating said real-time sensor data using statistical process control charting techniques to determine if a corresponding sensor is in control. 
 
   
   
     116. The computer-readable medium as set forth in  claim 98 , said method further comprising:
 computing a plurality of certainty factors for a corresponding plurality of possible faults.